Change in coreboot[4.11_branch]: cpu/x86/smm: Add overflow check

[Marc Jones (Code Review)]

Attention is currently required from: Nico Huber.
Hello Nico Huber,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/coreboot/+/50311

to review the following change.

Change subject: cpu/x86/smm: Add overflow check
......................................................................

cpu/x86/smm: Add overflow check

Rather bail out than run into undefined behavior.

Original-Change-Id: Ife26a0abed0ce6bcafe1e7cd8f499618631c4df4
Original-Signed-off-by: Nico Huber 
Original-Reviewed-on: https://review.coreboot.org/c/coreboot/+/38763
Original-Tested-by: build bot (Jenkins) 
Original-Reviewed-by: Patrick Rudolph 
Original-Reviewed-by: Angel Pons 
Original-Reviewed-by:

(cherry picked from commit 6d5f007813f6a2ffbdd6a633f31d207672eee2e1)
Signed-off-by: Marc Jones

Change-Id: I28e10d8836ab80c6fec9d3414c795c5e6ff312e8
---
M src/cpu/x86/smm/smm_module_loader.c
1 file changed, 2 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/11/50311/1

diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 0940e34..3ed20b7 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -203,6 +203,8 @@
    /* Adjust remaining size to account for save state. */
    total_save_state_size = params->per_cpu_save_state_size *
    			params->num_concurrent_save_states;
+	if (total_save_state_size > size)
+		return -1;
    size -= total_save_state_size;

/* The save state size encroached over the first SMM entry point. */